Which policy document provides guidance to all government agencies on classification, downgrading, declassification, and safeguarding of classified national security information?

a) National Industrial Security Program
b) Security Classification Guide
c) Freedom of Information Act
d) Controlled Unclassified Information

The Executive Order on Classified National Security Information, not listed in the options, but relevant to the context, governs classification, downgrading, declassification, and safeguarding of classified information.

Explanation:

The policy document that provides guidance to all government agencies on classification, downgrading, declassification, and safeguarding of classified national security information is known as the Executive Order on Classified National Security Information. This document establishes the framework for handling national security information in the United States and is periodically updated to reflect current practices and policies. While the options provided include important related concepts and laws, such as the Freedom of Information Act (FOIA) which allows for transparency and public access to government records, it is the executive orders specifically dealing with national security information, not provided in the multiple-choice options, that govern the classification system.